day-117.cpp

/*
  Add Digits


Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.

Example:

Input: 38
Output: 2 
Explanation: The process is like: 3 + 8 = 11, 1 + 1 = 2. 
             Since 2 has only one digit, return it.
Follow up:
Could you do it without any loop/recursion in O(1) runtime?
*/

// Simple while loop implementation in cpp

class Solution {
   public:
    int addDigits(int num) {
        int temp = num;
        while (temp > 9) {
            int answer = 0;
            while (temp != 0) {
                answer += (temp % 10);
                temp /= 10;
            }

            temp = answer;
        }

        return temp;
    }
};